By design, synchronizers will block the driver from completing their shift into any gear. And, for that matter, even shifting into a gear in the first place if the speed of the clutch disc, input shaft & various other components doesn’t match the speed of the gear they are shifting into. My expertise is modifying transmissions to shift at extremely high rpms, there is no equal. However it is crucial that your clutch is operating properly, with sufficient release to allow the clutch disc, input shaft & various other components to be “free” of the engine’s rotating speed thus allowing them to slow down and match the speed of the gear you are shifting into.
The synchros are NOT designed or capable of dealing with a clutch that doesn’t have enough release. If you are having trouble getting into any gears while the car is running or are experiencing blocking or “notchy” shifting; you must check your clutch to make sure that you have it properly adjusted or you will cause damage to the synchronizers that is not covered under warranty. Every effort has been taken to ensure that your transmission is capable of shifting at high rpms while retaining long synchro life. It is sole responsibility of the driver or installer to make sure that the clutch is properly adjusted so that is has sufficient release to allow the synchros to do their job without the clutch disc dragging on the flywheel/pressure plate assembly.